/Engine/Source/Runtime/Experimental/Iris/Core/Public/Iris/DataStream/DataStream.h
For each packet into which we have written data we are guaranteed to get a call to ProcessPacketDeliveryStatus when it's known whether the packet was delivered or not.
virtual void ProcessPacketDeliveryStatus ( [UE::Net::EPacketDeliveryStatus](API\Runtime\IrisCore\Iris\PacketControl\UE__Net__EPacketDeliveryStatus) Status, [FDataStreamRecord](API\Runtime\IrisCore\Iris\DataStream\FDataStreamRecord) const * Record )